1. Field of the Invention
The present invention relates in general to internal combustion engines, and more particularly, to the engines of a type having a front cover structure secured to a front end of a cylinder block thereof.
2. Description of the Prior Art
In order to clarify the task of the present invention, one known internal combustion engine of the above-mentioned type will be described with reference to FIG. 6 of the accompanying drawings, which is disclosed in Japanese Utility Model Second Provisional Publication No. 62-11303.
In FIG. 6, designated by numeral 102 is a cylinder block of an internal combustion engine. The cylinder block 102 has a longitudinal end which is designated by numeral 103.
Designated by numeral 102A is an oil inlet opening formed in the cylinder block 102, from which an oil passage (not shown) extends to an opening of the cylinder block 102 to which opening an oil filter (not shown) is connected from the outside.
Designated by numeral 101 is a front cover structure which is to be bolted to the longitudinal end 103 of the cylinder block 102. As shown, the front cover structure 101 has an oil pump 104 mounted to an inside portion thereof. Designated by numeral 110 is an oil outlet opening formed in the front cover structure 101, from which an oil passage (not shown) extends to an outlet portion of the oil pump.
The oil pump 104 is of internal gear type, comprising a drive gear 104A which is connected to a crankshaft (not shown) to be driven by the same and a driven gear 104B which is rotatably disposed about the drive gear 104A having a part thereof operatively engaged with the drive gear 104A. Designated by numeral 107 is an oil strainer which has an upper end connected to the oil pump 104 and a lower enlarged end placed in an oil pan (not shown) of the engine.
In operation, the oil pump 104 sucks thereinto the oil from the oil pan through the oil strainer 107 and pumps the oil, thus pressurized, into the oil passage of the front cover structure 101 and into the oil passage of the cylinder block 102 through the outlet opening 110 and the inlet opening 102A. The oil in the oil passage of the cylinder block 102 is then conducted to various portions of the engine through the oil filter.
However, due to its inherent construction, the arrangement possessed by the above-mentioned known front cover structure 101 has the following drawbacks.
First, because the oil filter is connected to the cylinder block 102, the oil passage from the oil inlet opening 102A to the opening to which the oil filter is connected is very complicated in structure. Furthermore, due to the complicated structure of the oil passage in the cylinder block 102, the oil flowing along the oil passage of the cylinder block tends to be overly heated by the heat possessed by the cylinder block 102. As is known, the overly heated oil reduces its viscosity and thus its lubricating activity.